There are known falling-arousal-level detection devices that determine from detected blinks any blinks of blink bursts that occur with an inter-blink interval within a specific time duration, and determine blinks accompanying a lengthy closed eye period of a specific duration or longer, so as to determine falling arousal level in an investigation subject from history data of blink burst blinks and blinks accompanying lengthy closed eye periods (see Patent Document 1).    Japanese Patent Application Laid-Open (JP-A) No. 2008-73335